Varicella zoster virus (VZV) is, by virological standards, one of the most successful of the human herpesviruses. It infects the majority of the population in childhood and decades later reappears to cause zoster (shingles) in the elderly. Both diseases are life-threatening in the immune compromised, and zoster causes long-term pain and severe ocular disease that can devastate vision. Despite the efforts of virologists, VZV remains a difficult virus to study, because the virus grows poorly outside the human host. Our research has focused on a critical subset of viral proteins that control viral gene expression, with the long-term objective that the elucidation of their functions will establish the foundations for novel antiviral strategies. We have previously focused on the key regulatory protein, IE62, which functions in the nucleus as the main activator of viral transcription. In this proposal, our studies extend to a viral protein kinase that we have discovered has a profound effect on the functions of IE62, by excluding it from the cell nucleus. We therefore hypothesize that the protein kinase is also involved in the control of gene transcription. In Specific Aim 1, we will test the hypothesis that the gene 66 protein kinase inhibits IE62 nuclear import by directly phosphorylating it and inhibiting binding of the nuclear import factors known as importins. The inhibited nuclear import by a viral kinase has not been reported for other herpesviruses, but is a model for a mechanism that is used by the host cell to control function through nuclear exclusion. In Specific Aim 2, we will test the hypothesis that host cell expression of gene 66 protein kinase will act as an 'intracellular vaccine', preventing VZV infection by inhibiting nuclear functions of IE62 made upon infection. Our results may establish a basis for using the kinase in an antiviral strategy targeted to VZV. Specific Aim 3 test the hypothesis that the gene 66 protein kinase targets IE62 through a specific amino acid motif, and that certain viral and cellular proteins with this motif are also phosphorylated by the protein kinase. These studies may elucidate other functional roles for the protein kinase in the course of VZV infection.